This invention relates to olefin polymerization processes and the resultant polymer products.
Ultra high molecular weight olefin polymers such as polyethylene usually have excellent properties, such as, for example, high impact strength and dimensional stability, low coefficient of friction, self-lubricating and are highly resistant to most chemicals. Thus, ultrahigh molecular weight polyethylenes are useful in many demanding and extremely critical applications, such as human joint replacements, gears, bullet proof vests, skis, and other applications. However, ultrahigh molecular weight polyethylenes can be difficult to process with conventional equipment. Since ultra high molecular weight polymer cannot be pelletized after leaving the reactor, the polymer must be sold as a fluff or a powder. Therefore, particle size and toughness of the resultant polymer is critical.
Many commercial methods are available to produce olefin polymers, such as polyethylene. One of the most economical routes to most commercial grades of olefin polymers is a loop/slurry process with a paraffin diluent wherein the polymerization process can be carried out at a temperature low enough that the resulting polymer is largely insoluble in the diluent. It is believed that commercially acceptable ultra high molecular weight ethylene polymers traditionally are made using a stirred tank process, in a heavy hydrocarbon diluent.